1. Field of the Invention
This invention relates to a two-component type adhesive agent for wood. Particularly, it relates to a two-component type adhesive agent for wood which comprises a polyvalentepoxy compound and an amino group-containing polymer modified with an alkylene imine and possessed of an activated hydrogen atom. More particularly, it relates to a two-component type adhesive agent for wood which enjoys a long pot life and, on being applied to wood and allowed to closs-link thereon at room temperature, imparts to the wood waterproofness and resistance to the effect of boiling and avoids defiling the wood.
2. Description of the Prior Art
Heretofore, vinyl acetate type emulsions and chloroprene type or styrene-butadiene type latexes have been used as adhesive agents for wood. Other adhesive agents of this class having urea resin or phenol resin incorporated therein for imporovement in waterproofness and resistance to the effect of boiling and adhesive agents of aqueous vinyl urethane produced by dispersion of isocyanate in a polymer emulsion containing an aqueous polyvinyl alcohol solution as disclosed in U.S. Pat. No. 3931088, etc. have been also put to use. Further, mixtures comprising a polymer containing an activated hydrogen atom capable of reacting with an epoxy group, a varying latex, and a compound containing at least two epoxy groups in the molecular unit thereof and mixtures comprising a polyvalentepoxy compound, an emulsion having a hydrazine derivative possessing at least two hydrazine residues dispersed in a polymer emulsion possessing a carboxyl group represented by an aldo group or a keto group, and a polyvinyl alcohol as essential components have been proposed as adhesive agents for wood.
Generally, an adhesive agent for wood by nature is expected to fulfil the following requirements:
(1) It should be capable of allowing required adhesion at room temperature.
(2) It should be capable of closs-linking at room temperature.
(3) It should possess a pot life sufficient from the practical point of view.
(4) It should possess highly satisfactory adhesive properties including adhesive power under normal conditions, waterproofness, thermal stability, and resistance to the effect of boiling.
(5) It should ensure safe use by exhibiting pH in the neutral region and avoiding inclusion of harmful substances such as formalin and organic solvent.
(6) It should possess constitution such that it excels in workability and the adhesive agent adhering to a machine used in application to wood can be easily removed by washing with water.
The aforementioned adhesive agents for wood formed of vinyl acetate type emulsions and chloroprene type or styrene-butadiene type latexes, however, are deficient in waterproofness. The adhesive agents of this class having urea resins or phenol resins additionally incorporated therein for improvement in waterproofness necessitate an extra heating step and prove to be incomplete in the ability to resist the effect of boiling. The adhesive agents formed of aqueous vinyl urethane, though excelling in waterproofness and resistance to the effect of boiling, suffer from conspicuous effervescence and viscosity, offer only an insufficient pot life, and betray a poor workability in the process of application to wood. The adhesive agents for wood formed of a mixture comprising a compound containing an activated hydrogen atom capable of reacting with an epoxy group, a varying latex, and a compound containing at least two epoxy groups in the molecular unit thereof are highly satisfactory in workability but unsatisfactory in resistance to the effect of boiling because they use an adhesive layer which combines a continuous layer of latex and a solidifying system. In the case of the adhesive agents formed of a mixture comprising a polymer emulsion having a hydrazine derivative possessing at least two hydrazine residues dispersed in a polymer emulsion possessing a carbonyl group represented by an aldo group or a keto group, an epoxy compound, and a polyvinyl alcohol as essential components, when hydrazine hydrate and other hydrazine derivative are used, the adhesive agents in the process of storage pose the problem of toxicity due to the free hydrazine formed by hydrolysis of the hydrazine derivative. Further, these adhesive agents are not satisfactory in terms of the ability to resist the effect of boiling.
An object of this invention, therefore, is to provide a novel two-component type adhesive agent for wood.
Another object of this invention is to provide a two-component type adhesive agent for wood which fulfils the requirements expected of an adhesive agent for wood, alleviates the effects of the adverse properties of the conventional wood-grade adhesive agents, enjoys a long shelf life, allows required adhesion at room temperature, produces a solidified adhesive layer excelling in waterproofness and resistance to the effect of boiling, and avoids defiling the wood.